Patent GB-403150-A (GB)
Title: Improvements in or relating to the separation of materials of different specific gravities
IPC: B03B5/38
Filed: 1932-07-08
Abstract: 403,150. Washing granular materials. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London.-(Chance, T.; Merion, Pennsylvania, U.S.A.) July 8, 1932, No. 19355. [Class 82 (ii).] In the sand-flotation process coarse sand and refuse are withdrawn from the separating chamber through an upward current classifier containing a fluid medium of lower specific gravity than that of the fluid mass in the separating chamber. The coarse sand and refuse are passed to a screen or other means for separating the sand and water from the refuse and the separated sand is returned to the upper part of the separating chamber, the rate of withdrawal of coarse sand through the classifier being adjusted to compensate for any segregation or stratification of sand taking place in the chamber. A mixture of sand and floated material, e.g. coal, may be removed from the top of the separating chamber and this sand also, after separation from the coal &c., may be returned to the upper part of the chamber. The separating chamber 1, in which a mixture of sand and water is maintained as a substantially homogeneous mixture by combined hydraulic and mechanical agitation, is superposed on a classifier column 3 in which an upward current of fluid having a lower specific gravity than the mixture in the chamber 1 is maintained. Below the column 3 is a refuse chamber 8 having an air vent 10 and closed by gates 6 7. The lighter material which floats in the suspension of sand and water, e.g. coal, is passed mixed with sand and water over a screen 11, the sand and water passing into a sump 13, Fig. 1, from which a thickened mixture of sand and water is withdrawn by a pump 14 and returned to the top of the chamber 1. The mixture of refuse and coarse sand which passes through the classifier column 3 into the refuse chamber 8 is discharged on to a screen 12, the sand and water passing through to a sump 22 from which they are returned by a pump 23 to the chamber 1, either directly to the top by a pipe 24, indirectly to the top through a pipe 25 and the sump 13 and pump 14, or, in certain cases, to a lower point in the chamber by a pipe 26. An annular baffle 21 is provided in the sump 13 to prevent the overflow of sand carried by air bubbles. The water overflows into a receptacle 15 from which some is withdrawn by a pump 16 and divided between screen sprays 17 18, a valved inlet 4 for producing the upward current in column 3, and valved inlets 5 for hydraulic agitation of the suspension in the chamber 1. Water also passes from the receptacle 15 through a pipe 29 to refill the refuse chamber 8 after it has been emptied, a check valve 30 and valve 9 being provided on the pipe 29. In the form shown in Fig. 2 the sand and water from the screens 11 12 pass to a common sump 13<1>, a thickened suspension of sand and water being returned to the chamber 1 by a pump 141. In this form the agitation of the suspension in chamber 1 is controlled so that a clear layer of water floats on the suspension, as described in Specification 119,038, [Class 82 (ii), Washing granular &c.], and the refuse chamber 8 is preferably refilled by the provision of a parting member 27 to pass the clear water through the pipe 29 to the chamber 8. The water from this source may be supplemented or replaced by water pumped from the receptacle 15. Additional water is supplied to the system by a final spray 20 for the clean coal.